Method of making a catheter

ABSTRACT

Electro-conductive catheters and methods of manufacture thereof.

United States Patent 1191 3,731,376

Ackerman 1 May 8, 1973 [54] METHOD OF MAKING A CATHETER [56] ReferencesCited [75] Inventor: Bernard Ackerman, Metuchen, UNITED S S PATENTS NJ.3,264,017 8/1966 Legarde ..29/461 X 3,340,493 9 1967 Fisher et a1. ..33961 [73] AgslgmZ Electm'cathem' Corlmmfion, 3,333,045 7/1965 Fisher et al174 20 y 3,426,316 2 1969 Olson ..339 151 22 Filed; Jam 22 19713,198,059 8/1965 Pfaneuf ....29/592 X 3,244,174 4 1966 Wesbey et al. 128/4 1 s 1 1 pp NW 108,742 3,348,548 10 1967 Cardack ..128/418 3,466,7429/1969 Sinclair..... ....29 624 x Remed Applcam" 3,474,791 10/1969Bentov ..128/418 [62] Division of Ser. N0. 718,434, April 3, 1968, Pat.No.

3,590,822. Primary Examiner-Charles W. Lanham Assistant Examiner-J. W.Davie U.S. CI. 8 Att rney A-mand Lackenbach et aL [51] Int. Cl. ..H0lb13/00 [58 Field 61 Search ..29/630 F, 461, 624, [57] ABSTRACTElectro-conductive catheters and methods of manufacture thereof.

13 Claims, 5 Drawing Figures PATENTEDHAY 8 I973 CABLE INSERTED THROUGHELECTRODE END PORTION OF CABLE SPREAD APART ELECTRODE MOVED o DISTAL ENDPORTION 0;:

CABLE TO COMPRESS SPREAD APART STRANDS ELEC TRODE. SOLDERED T0 CABLEDISTAL END PORT/0N SHEATH POSIT/DNED OVER CAB PROXIMAL END OF CABLESOLDERED TOG DlsmL END POSITIONED IN FORMING SLEEVE DISTAL END HEATED T0FLOW SLEEVE END OVER ELECTRODE AND INTO CABLE PROXIMAL E SHEAT'H HEATEDTO FLOW INTO CABLE INVENTOR. BERNARD ACKERMAN METHOD OF MAKING ACATHETER This is a division of application Ser. No. 718,434, filed Apr.3, 1968, now US. Pat. No. 3,590,822.

This invention relates to catheters and, more particularly, toelectro-conductive catheters and to methods of manufacture thereof.

It is a primary object of the present invention to provide novelelectro-conductive catheters and novel methods of manufacture thereof.

Another primary object of the present invention, in addition to each ofthe foregoing objects, is the provision of such novel cathetersparticularly adapted for use, for example, as a pacing electrode.

Yet another primary object of the present invention, in addition to eachof the foregoing objects, is the provision of such catheters comprisingan electrically conductive core and electrically insulating sheath.

Still another primary object of the present invention, in addition toeach of the foregoing, is the provision of such catheters wherein thecore comprises a wire cable and the sheath comprises a low frictionfluid impervious, easily cleaned and nontoxic substance.

Another and yet still further primary object of the present invention,in addition to each of the foregoing objects, is the provision of suchcatheters wherein the sheath comprises a thermoplastic material.

A still further primary object of the present invention, in addition toeach of the foregoing, is the provision of such catheters furthercomprising an electrode tip having a smoothly rounded nose securely andfirmly connected with the core and extending outwardly of the sheath. IAnother and yet still further primary object of the present invention,in addition to each of the foregoing, is the provision of novel methodsof forming such a tip and of connecting such a tip with such a core.

In addition to each of the foregoing, it is also a primary object of thepresent invention to provide such catheters wherein the sheath issecurely bonded with the electrode and adjacent core at the distal endand with the core at the proximal end.

Yet further, still another primary object of the present invention, inaddition to each of the foregoing, is the provision of novel methods ofbonding the sheath to the core and electrode.

Another and still. further primary object of the present invention, inaddition to each of the foregoing, is the provision of such catheterswherein the core is sealed at both the distal and proximal ends of thesheath to preclude passage of fluids therethrough.

A still further primary object of the present invention, in addition toeach of the foregoing, is the provision of such catheters wherein thedistal and proximal end portions of the sheath are caused to flowbetween to seal and bond with the individual core strands at the distaland proximal ends.

Yet another primary object of the present invention, in addition to eachof the foregoing, is the provision of novel methods of bonding thesheath to the core at the distal and proximal ends.

The invention resides in the combination, construction, arrangement anddisposition of the various component parts and elements incorporated inimproved catheters constructed in accordance with the principles of thisinvention and in methods of manufacture thereof. The present inventionwill be better understood and objects and important features other thanthose specifically enumerated above will become apparent whenconsideration is given to the following details and description, whichwhen taken in conjunction with the annexed drawing describes, discloses,illustrates and shows a preferred embodiment or modification of thepresent invention and what is presently considered and believed to bethe best mode of practicing the principles thereof. Other embodiments ormodifications may be suggested to those having the benefit of theteachings herein, and such other embodi- 'ments or modifications areintended to be reserved especially as they fall within the scope andspirit of the subjoined claims.

IN THE DRAWING FIG. 1 is a process flow chart depicting the varioussteps which may be utilized in producing catheters in accordance withthe present invention;

FIG. 2 is an enlarged illustration of an end portion of a core cable andan electrode for use therewith showing one step of the method;

FIG. 3 is a view similar to FIG. 2 illustrating a succeeding step in themethod;

FIG. 4 is a view similar to the preceding figures illustrating a yetfurther-step in the method; and

FIG. 5 is a view similar to the preceding illustrating a yet stillfurther step in the method.

With reference now to the drawing, catheters constructed in accordancewith the principles of the present invention may comprise anelectrically conductive elongate and bodily flexible core 10, anelectrically conductive electrode 12 electrically and mechanicallyconnected therewith adjacent one end portion thereofand an electricallynon-conductive and chemically substantially inert sheath 14 extendingsubstantially entirely of the core 10. The core 10, electrode 12 andsheath l4 accordingly define a catheter constructed in accordance withthe principles of the present inventionand designated generally by thereference character 16.

Catheters constructed in accordance with the present invention areparticularly suitable for use as cardiac pacing electrodes. Hence, thecatheters are intended to be .inserted through the veinous system intothe heart to provide electrical impulses directly thereto. To besuitable for such utilization, there are several criteria which must befulfilled. The catheter must be of sufficient flexibility as to becapable of easy passage through the veinous system. The outer surfaceand the nose portion of the catheter must be sufficiently smooth as topreclude any chance of trauma or injury to the patient's veins or heart.The catheter must be capable of being sterilized. Any possibility ofbreakage or separation of the tip or electrode from the remainder of thecatheter must be minimized. The catheter must be substantiallyimpervious to body or other fluids to prevent any infection orcontamination. For ease in passing the catheter through the veinoussystem and positioning the tip or electrode portion thereof at thedesired location, the catheter should be capable of being easily steeredfrom the proximal end. This steering may be accomplished by providing aslight curvature to the tip portion and constructingthe catheter toenable the smooth transmission of torque.

therethrough to enable a rotation of the proximal end to direct thecurved portion in a desired direction.

The core may be of either stranded or solid construction. However, inorder to provide the requisite flexibility and torque response, the core10 preferably comprises a plurality of wire strands 18 twisted or laidtogether to define a wire rope or cable. The strands 18 may also bewoven or braided together. However, it has been found that a twistedwire rope type of construction utilizing 21 wires twisted in regular lay7 X 3 is especially suitable. By regular lay 7 X 3 is meant that therope comprises seven strands twisted with a righthand lay, each of theseven strands comprising three wires twisted together in a lefthand lay.It has been found that such a wire rope fabricated of brass coatedstainless steel wire and having an overall diameter of approximately0.023 inches forms a suitable core.

The electrode 12 may similarly be fabricated of substantially anymaterial and may, for example, comprise a stainless steel sleeveapproximately 3/16 inch long having a generally axial bore of slightlygreater diameter than that of the wire rope or core 10. The electrode 12may be assembled with the wire rope or core 10 by inserting the distalend portion of the wire rope or core 10 through the bore 20 of theelectrode 12 to extend outwardly thereof a distance slightly greaterthan the length of the electrode 12. Then, the wires and strands of thewire rope or core 10 may be spread apart, untwisted, and separated toflair outwardly, as illustrated in FIG. 2. The electrode 12 may then bemoved relative to the wire rope or core 10 to aposition adjacent thedistal end portion thereof so as to overlie the spread apart wires orstrands thereof, as illustrated in FIG. 3. The resilience of the wiresof the rope or core 10 after having been spread apart and thenpositioned or disposed within the electrode 12 will engage the bore 20thereof while remaining somewhat separated one from the other. Theelectrode 12 and associated distal end portion of the wire rope or core10 may then be firmly and securely electrically and mechanicallyinterconnected, as by silver solder. The solder may be applied in anydesired manner, as by dipping the electrode and associated distal endportion of the core 10.

into a molten pool of solder. The solder will flow between the wires orstrands of the rope or core 10 and will firmly bond the wires togetherand to the electrode 12. The distal end of the electrode 12 will berounded, as shown, by the solder. It is exceedingly important, instructures of this kind, that there be absolutely no danger of theelectrode 12 becoming separated from the wire rope or core 10 since, ifit should become separated, it would be left within the circulatorysystem of the patient where it could cause substantial injury or death.It is believed readily apparent that the strong mechanicalinterconnection between the wires of the wire rope or core 10 and theelectrode 12 formed in accordance with the present invention providesexceptional strength for effectively precluding any danger of accidentalseparation of the electrode 12 and the wire rope or core 10.

With reference now to FIG. 4, the sheath 14 may then be positioned onthe wire rope or core 10 with the distal end thereof generally adjacentto or abutting the electrode 12. The sheath 14 may, for example,comprise a chemically and organically substantially inert material. Thesheath 14 may further comprise a material which presents, or is capableof presenting, a substantially smooth, low friction surface. Yetfurther, the sheath 14 may comprise a material which is substantiallynon-porous and which may be sterilized, either by heat or chemicalaction. The sheath 14 may, for example, comprise polyethylene tubing.The sheath 14 may be of slightly lesser longitudinal extent than that ofthe wire rope or core 10 so that when the sheath 14 is positionedthereon and adjacent the electrode 12, the proximal end of the wire ropeor core 10 will project outwardly therefroma short distance, forexample, several centimeters, as illustrated in FIG. 4. The proximal endportion of the wire rope or core 10 may then be dipped or otherwisesoldered, to securely bond the wires or strands thereof together.

To enable the transmission of torque along the catheter from theproximal to the distal end, especially to enable easy and accuratesteering thereof, and to retain the sheath 14 positioned on the wirerope or core 10, at least the end portions of the sheath 14 should besecured with the wire rope or core 10. While the sheath 14 may besecured with the core or wire rope 10 substantially entirelylongitudinally thereof, it is sufficient that the sheath 14 be securedwith the wire rope or core 10 at or adjacent the distal and proximal endportions thereof. Moreover, it is preferable that the catheter, andparticularly the interstices between the wires and strands of the wirerope or core 10 be sealed to preclude the absorption or transmission offluids therethrough, especially at the distal end portion, and to reduceor eliminate possible site for bacterial or other organic activity.

The sheath 14 may, for example, comprise a thermoplastic material, suchas polyethylene and the end portions thereof may be softened, as by theapplication of heat thereto, and, while softened caused to move or flowin such a manner as to fill the interstices of the wire rope or core 10to preclude the passage of fluid therethrough and to secure the endportions of the sheath 14 against movement relative to the wire rope orcore 10. Moreover, by appropriately working or forming the softeneddistal end portion of the sheath 14, it may be caused to flow intointimate contact with the electrode 12 to form a sealed and smoothjuncture therewith.

Accordingly, and with reference now to FIG. 5, the distal end portion ofthe sheath 14 may be heated or otherwise softened and formed or flowedabout the proximal end portion of the electrode 12 and through theinterstices of the adjacent portion of the wire rope or core 10 bypositioning the distal end portion of the catheter 16, that is, theelectrode 12 and the adjacent portions of the wire rope or core 10 andsheath 14 within a forming sleeve 22 and applying heat thereto. Thesleeve 22 may, for example, comprise a tapered portion 24 adapted toclosely fit over the electrode 12 to define therewith a narrow taperedgap extending generally annularly about at least the proximal endportion thereof, as shown. Accordingly, when the distal end portion ofthe sheath 14 is heated, the plastic material will melt and flow intothat tapered annular gap and into and through the portion of the wirerope or core 10 adjacent the electrode 12 which, as heretofore pointedout, comprises loosened or slightly separated wire or strand portions.Hence, the sheath 14 may be securely bonded with the electrode 12 andwith the adjacent portion of the wire rope or core while being smoothlytapered by the forming sleeve 22 to enable the transmission of torque,to provide a smooth surface, and to positively seal againstcontamination or transmission of fluids. The degree of heat appliedshould be sufficient to cause the plastic material to flow, asheretofore described, without introducing decomposition thereof.

The proximal end portion of the catheter 16 may then be disposed withina similar forming sleeve and heated or otherwise softened to cause thematerial of the sheath 14 to flow into and through the wire rope or core10 to bond and seal the proximal end of the catheter 16. A'slight curvemay then be formed at the distal end of the catheter as an aid insteering the catheter through body passages by inserting the distal endinto a curved forming tube and heating the distal end portion andsubsequently pulling it while restraining it in such curvedconfiguration, or by substantially any other setting process.

Accordingly, it is believed readily apparent that catheters constructedin accordance with the present invention fulfill the objects hereinaboveset forth. Such catheters will be flexible while yet being torqueresponsive and easily steered. The entire catheter will be smooth andsealed against contamination, the electrode will be rounded, smooth andsealed by the silver solder bath and the proximal end portion of theelectrode will be sealed, smooth and tapered by the overlying portion ofthe sheath formed in the tapered fonning sleeve. The sheath will bebonded to the electrode and to the adjacent portion of the wire rope orcore. The proximal end portion of the sheath will be similarly bonded tothe wire rope or core and the proximal end portion of the wire rope orcore will be soldered together to preclude unravelling and to enableready connection thereof with an appropriate pacing device, or the like.The tip or electrode will be positively and securely associated with thewire rope or core substantially entirely eliminating any danger of thetip or electrode being inadvertently separated therefrom. The entirecatheter will be readily sterilizable and present minimal possiblecontamination sites.

While the invention has been described, disclosed, illustrated and shownin terms of a preferred embodiment or modification which it has assumedin practice, the scope of the invention should not be deemed to belimited by the precise embodiments or modifications herein described,disclosed, illustrated or shown, such other embodiments or modificationsas may be suggested to those having the benefit of the teachings hereinbeing intended to be reserved especially as they fall within the scopeand breadth of the claims here appended.

I claim:

1. Method of manufacturing a catheter comprising at least the steps offorming a smooth nose at a distal end of an elongate bodily flexiblecore of stranded wire, positioning a sheath having distal and proximateend portions over substantially the entire longitudinal extent of thecore, and securing the end portions of the sheath with the core todefine a bodily flexible catheter adapted to be readily rotated forsteering, or the like,

wherein said step of securing comprises the step of sealing theinterstices between the core wires.

2. Method defined in claim 1 wherein the step of forming comprisespositioning a metal sleeve on the distal end portion of the core andsoldering the sleeve with the core to define an electrode.

3. Method defined in claim 2 wherein said step of positioning comprisesthe step of separating the core prior to soldering to enhance bondingbetween the sleeve and the core.

4. Method defined in claim 3 wherein said step of soldering provides ablunt, rounded end to the electrode, whereby said smooth nose isdefined.

5. Method defined in claim 4 wherein said step of securing comprisessecuring the sheath with the nose.

6. Method defined in claim 2 wherein said step of positioning comprisesthe steps of passing the distal end portion of the core through thesleeve, spreading the projecting end portion of the core laterallyoutwardly of the sleeve and withdrawing the core until the distal end isentirely within the sleeve and engaged with the interior thereof.

7. Method defined in claim 2 wherein said step of soldering comprisesdip soldering in a molten bath of silver solder.

8. Method defined in claim 2 comprising the additional step of applyingsolder to a proximal end portion of the core.

9. Method defined in claim 3 wherein the core comprises twisted regularlay wire rope, and said step of positioning comprises at least the stepof untwisting.

10. Method defined in claim 1 wherein said sheath comprises athermoplastic material, and said step of securing comprises the step ofheating the end portions of the sheath to enable said end portions toflow around and between the wires of the core at a corresponding endportion thereof to form a bond therewith.

11. Method defined in claim 10 further comprising separating the wiresof the core at the end portion to be sealed.

12. Method defined in claim 10 further comprising the additional step ofpositioning said end portions within a sleeve during such heating andsealing.

13. Method defined in claim 12 further comprising laterally confiningthe sheath material by said sleeve.

1. Method of manufacturing a catheter comprising at least the steps of forming a smooth nose at a distal end of an elongate bodily flexible core of stranded wire, positioning a sheath having distal and proximate end portions over substantially the entire longitudinal extent of the core, and securing the end portions of the sheath with the core to define a bodily flexible catheter adapted to be readily rotated for steering, or the like, wherein said step of securing comprises the step of sealing the interstices between the core wires.
 2. Method defined in claim 1 wherein the step of forming comprises positioning a metal sleeve on the distal end portion of the core and soldering the sleeve with the core to define an electrode.
 3. Method defined in claim 2 wherein said step of positioning comprises the step of separating the core prior to soldering to enhance bonding between the sleeve and the core.
 4. Method defined in claim 3 wherein said step of soldering provides a blunt, rounded end to the electrode, whereby said smooth nose is defined.
 5. Method defined in claim 4 wherein said step of securing comprises securing the sheath with the nose.
 6. Method defined in claim 2 wherein said step of positioning comprises the steps of passing the distal end portion of the core through the sleeve, spreading the projecting end portion of the core laterally outwardly of the sleeve and withdrawing the core until the distal end is entirely within the sleeve and engaged with the interior thereof.
 7. Method defined in claim 2 wherein said step of soldering comprises dip soldering in a molten bath of silver solder.
 8. Method defined in claim 2 comprising the additional step of applying solder to a proximal end portion of the core.
 9. Method defined in claim 3 wherein the core comprises twisted regular lay wire rope, and said step of positioning comprises at least the step of untwisting.
 10. Method defined in claim 1 wherein said sheath comprises a thermoplastic material, and said step of securing comprises the step of heating the end portions of the sheath to enable said end portions to flow around and between the wires of the core at a corresponding end portion thereof to form a bond therewith.
 11. Method defined in claim 10 further comprising separating the wires of the core at the end portion to be sealed.
 12. Method defined in claim 10 further comprising the additional step of positioning said end portions within a sleeve during such heating and sealing.
 13. Method defined in claim 12 further comprising laterally confining the sheath material by said sleeve. 